Analysis of In-Vehicle Black Carbon Exposure and Trip Characteristics Using GPS Logs and Diaries

Poster SP-26 presented at ISEE 2012 Seattle, USA. Title: Analysis of In-vehicle Black Carbon Exposure and Trip Characteristics Using GPS Logs and Diaries Abstract: Background: Global Positioning Systems (GPS) are being used more frequently in health research. To limit respondent burden, and because of technical problems with the development of miniaturized air quality sensors; exposure is determined afterwards by linking GPS traces with air pollution models or nearby monitoring stations. In-vehicle exposure may however be not only related to yearly averaged outdoor concentrations. Objectives: To investigate whether the levels of in-vehicle Black Carbon (BC) concentrations are influenced by trip duration, hour of the day, traffic intensities, and spatial parameters like degree of urbanization or road type. Methods: Personal exposure measurements were done using µ-aethalometers, trip diaries and GPS devices. More than 1000 car-trips were evaluated in Flanders, Belgium. GPS coordinates were assigned to road segments to allow BC concentrations to be linked with trip and road characteristics. Results: Due to loss of signal, technical issues or participant’s error, 30% of all car trips had no GPS coordinates. If the distance between a GPS point and the closest road with known traffic intensities was larger than 30m, the observation was omitted (23% of all recorded coordinates). Average BC concentrations on highways are comparable to concentrations on urban roads (8.3 µg/m3), but almost double the concentrations on rural roads (4.7 µg/m3). BC concentrations are elevated at lower speeds (